In related art, audio encoding technologies that compress audio signals (sound sources of voice, music, and the like) have been developed. For example, as the audio encoding technologies, there are an advanced audio coding (MC) system, a high efficiency-advanced audio coding (HE-AAC) system, and the like. The MC system and the HE-AAC system are each one of moving picture experts group (MPEG)-2/4 audio standards of International Organization for Standardization/International Electrotechnical Commission (ISO/IEC), and are widely used for purposes of broadcasting such for example as digital broadcasting or the like.
In broadcasting applications, audio signals may need to be transmitted under the constraint of a limited transmission bandwidth. Therefore, when audio signals are to be encoded at a low bit rate, it is not possible to encode audio signals in all of frequency bands, and thus bands in which to perform encoding may need to be selected. Incidentally, in general, in the MC system, about 64 kbps or less may be regarded as a low bit rate, and about 128 kbps or more may be regarded as a high bit rate. Japanese Laid-open Patent Publication No. 2007-193043, for example, discloses a technology that performs encoding while omitting audio signals having less than a given power so that a given bit rate is not exceeded.